Biology Chemistry Computer Engineering Electronics Mathematics Physics Science Home

UNIT 1:  CELLULAR FUNCTIONS

B.  Carbohydrates

SUGARS AND STARCHES

·         the major backbone of these molecules is the carbon atom

·         the structure of these kinds of molecules consists of carbon, hydrogen, and oxygen

·         simple sugars (monomers) are known as monosaccharides

·         the ending “ose” is common in the names of saccharides

·         a typical example of a monosaccharide is glucose, others include fructose, and galactose

·         the structural formula for glucose is shown in Figure 1.14, p. 13

·         when two monosaccharides are linked together, a disaccharide is made

·         sucrose (table sugar – Figure 1.16, p. 14), maltose (Figure 1.16, p. 14), and lactose (sugar in milk) are examples of disaccharides

·         table sugar is the combination of the two monosaccharides glucose and fructose

·         polysaccharides are made by linking up many units of monosaccharides

·         the process of making long-chained molecules in biology is called dehydration synthesis (or condensation reaction)

·         as Figure 1.17, p. 14 illustrates, water is pulled out from two monomer units -- the hydrogen of one unit reacts with the hydroxide        (-OH) of another unit, to make water, thus the name “dehydration” synthesis

·         the reverse reaction is called hydrolysis – this is where water is splits and is used up to break the bond that links the two monomer units together, yielding two smaller products

·         some important polysaccharides are starch, glycogen, and cellulose (Figure 1.18, p. 15)

·         starch is an energy storage molecule in plants and a common source of energy for animal cells

·         glycogen is the short-term energy storage molecule in human liver

·         cellulose is the molecule that makes up plant cell walls

·         the unit that makes each of these polymers is the same – glucose

·         the difference between these polymers is the structural manner in which each glucose monomer is linked to one another

·         polysaccharides are broken down via hydrolysis reactions, however, special helper molecules, called enzymes, are necessary to break up the linkages a specific locations in the chain

DEMO – MOLECULAR BUILDING MODELS – students build glucose and fructose, then sucrose, using model kits

Homework:  1-4, p. 16